Accretion disk coronae of Intermediate Polar Cataclysmic Variables - 3D: MagnetoHydro-Dynamic modeling and thermal X-ray emission
Journal
Date Issued
2017
Author(s)
Abstract
IPCVs contain a magnetic, rotating white dwarf surrounded by a magnetically
truncated accretion disk. To explain their strong flickering X-ray emission,
accretion has been successfully taken into account. Nevertheless, observations
suggest that accretion phenomena could not be the only process behind it. An
intense flaring activity occurring on the surface of the disk may generate a
corona, contribute to the thermal X-ray emission and influence the system
stability. Our purposes are: investigating the formation of an extended corona
above the accretion disk, due to an intense flaring activity occurring on the
disk surface; studying its effects on the disk and stellar magnetosphere;
assessing its contribution to the observed X-ray flux. We have developed a 3D
MHD model of a IPCV. The model takes into account gravity, disk viscosity,
thermal conduction, radiative losses and coronal flare heating. To perform a
parameter space exploration, several system conditions have been considered,
with different magnetic field intensity and disk density values. From the
results of the evolution of the model, we have synthesized the thermal X-ray
emission. The simulations show the formation of an extended corona, linking
disk and star. The flaring activity is capable of strongly influencing the disk
configuration and its stability, effectively deforming the magnetic field
lines. Hot plasma evaporation phenomena occur in the layer immediately above
the disk. The flaring activity gives rise to a thermal X-ray emission in both
the [0.1-2.0] keV and the [2.0-10] keV bands. An intense coronal activity
occurring on the disk surface of an IPCV can affect the structure of the disk
depending noticeably on the density of the disk and the magnetic field of the
central object. Moreover, the synthesis of the thermal X-ray fluxes shows that
this flaring activity may contribute to the observed thermal X-ray emission.
Volume
600
Start page
A105
Issn Identifier
0004-6361
Rights
open.access
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